SCIENCE SKILLS 2.3
Chapter Two: Science Skills
2.1 Mass and Volume
2.2 Density
2.3 Graphing
2.4 Solving Problems
Section 2.3 Learning Goals
Use graphs to create a visual
representation of data.
Analyze trends on a graph.
Explain the difference between a direct
relationship and an inverse relationship.
Investigation 2C
Thickness of Aluminum Foil
Key Question:
What is the thickness of
aluminum foil?
2.3 Graphing
 A graph is a visual way to organize
data.
 A scatterplot
or XY graph is
used to see if
two variables
are related.
2.3 Graphing
 A bar graph
compares data
grouped by a
name or
category.
2.3 Graphing
 A pie graph
shows the
amount each
part makes of
up of the whole
(100%).
2.3 Graphing
 A “connect-the-dots” line graph is
often used to show trends in data
over time.
2.3 How to make an XY graph
Scatterplots show how a change in one
variable influences another variable.
The independent variable is the variable
you believe might influence another
variable.
The dependent variable is the variable that
you hope will change as a result of the
experiment.
2.3 How to make an XY graph
Pressure is critical to safe diving.
How does an increase in depth affect
the pressure?
What sort of graph would best show
the relationship between pressure
and depth?
2.3 How to make an XY graph
1. Choose x and y-axis
 Depth is the independent variable = x axis
 Pressure is the dependent variable = y axis
2. Make a scale
 Most graphs use ones, twos, fives or tens
 OR calculate the value per box
3. Plot your data
4. Create a title
* Exception- when time is a variable
2.3 Identifying graph relationships
In a direct
relationship,
when one
variable
increases,
so does the
other.
The speed and distance variables show
a direct relationship.
2.3 Identifying graph relationships
When there is
no relationship
the graph
looks like a
collection of
dots.
No pattern appears.
2.3 Identifying graph relationships
In an
inverse
relationship,
when one
variable
increases,
the other
decreases.
2.3 Reading a graph
What is the speed of the car at 50 cm?
1. Find the known value on the x axis
 Position = 50 cm
2. Draw a line vertically upward from 50 cm
until it hits the curve.
3. Draw a line across horizontally to the yaxis from the same place on the curve.
4. Read the speed using the y axis scale.
 Speed = 76 cm/s